A cyclone is caused by atmospheric disturbances around a low-pressure area and is usually accompanied by violent storms and severe weather conditions.
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain.
Depending on its location and strength, a tropical cyclone is referred to by names such as hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, and simply cyclone.
Hurricane – Atlantic Ocean & northeastern Pacific Ocean,
Typhoon – Northwestern Pacific Ocean,
Willy Willy – Western Australian Coast,
Cyclone – South Pacific or Indian Ocean.
The Tropical cyclones require certain conditions for their formation such as:
-> Tropical cyclones typically form over large bodies of relatively warm water. They derive their energy through the evaporation of water from the ocean surface, which ultimately re-condenses into clouds and rain when moist air rises and cools to saturation.
-> A source of warm and moist air derived from tropical oceans with sea surface temperature normally near to or in excess of 27°C.
-> Winds near the ocean surface blowing from different directions converging and causing air to rise and storm clouds to form.
-> The low wind shear (wind which does not vary greatly with height) allows the storm clouds to rise vertically to high levels.
-> Coriolis force induced by the rotation of the Earth. Due to this induced force, once a cluster of storm clouds starts to rotate, it becomes a tropical depression and if it continues to develop, it becomes a tropical storm and later a cyclone/ super cyclone. (Blowing counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere).
-> The deep depression in the west of Sri Lanka and south of Kanyakumari intensified and resulted in a cyclonic storm Ockhi.
What is Cyclone Ockhi?
-> The name Ockhi is coined by Bangladesh.
-> According to Hurricane Research Division, tropical cyclones are named to provide ease of communication between forecasters and the general public regarding forecasts, watches, and warnings.
-> Cyclone Ockhi was the most intense tropical cyclone in the Arabian Sea since Cyclone Megh in 2015.
-> Ockhi originated as a low pressure area in the Gulf of Thailand.
-> Due to favourable conditions, it traversed the southern part of the Bay of Bengal, transforming into a deep depression.
-> As a deep depression, it caused damages to property and life in Sri Lanka.
-> Due to moisture and warmer temperatures between Sri Lanka and Kanyakumari (Cape Comorin) in mainland India, it transformed into a cyclone.
-> Close to Kanyakumari in mainland India, Cyclone Ockhi changed its path and headed towards Lakshadweep in the Arabian Sea, gaining strength and transforming into a super cyclone.
-> Ockhi dissipated near the south coast of Gujarat in India , due to prevailing conditions, even before entering the coast.
Why Cyclone Ockhi is Unique:
-> Cyclone Ockhi is noted for its very unusual course, originating in the Gulf of Thailand and ending near the coast of Gujarat in western India, travelling nearly 4000 nautical miles.
-> Mostly Arabian sea cyclones are local ones however Ockhi originated near South-Western Sri Lankan coast and travelled northwestern direction towards Indian coast, which is rare.
-> Generally cyclones in Arabian sea are not devastating however Ockhi is categorised as level 3 storm with wind speed of 155-160 km/hr. This is strange.
-> Instead of making landfall on the eastern coast, it proceeded towards the Lakshadweep islands and took a north-easterly turn towards Maharashtra and Gujarat coastline where cyclone are very rare.
Reasons for why Bay of Bengal has more cyclones than Arabian sea:
- Peninsular Landmass: The cyclones originating from the Bay of Bengal side are not able to sustain while travelling above the peninsular landmass due to absence of energy of evaporation and weakens while reaching the Eastern coast.
- Temperature difference: Bay of Bengal water is hotter than Arabian sea making it favourable for cyclones.
- Proximity with Pacific ocean: The low pressure system originating from the pacific ocean also travel towards left to Bay of Bengal and hit the western coast from Bay of Bengal.
- Direction of the cyclones: The direction of the low pressure system are from right to left, hence the Arabian sea originating cyclones are not able to hit the coastal areas.
- Flow of Jet streams: It increases the adversity of cyclones in Bay of Bengal.
Difference between Tropical and Temperate Cyclone:
- LATITUDE: Tropical cyclone is confined between 5 to 30* N&S of the equator, whereas temperate cyclone originates between 30 to 60* N&S of the equator .
- ORIGINATING ELEMENT: Temperature & Coriolis force plays vital role in the origin of tropical cyclone. In case of temperate cyclone, it is frontogenesis plays important driving force (occluded front).
- TYPES OF CLOUD ASSOCIATED: Wide range of clouds are associated with the temperate cyclone. While in the case of tropical cyclone the cloud composition is mainly dominated by cumulonimbus clouds .
- EYE: Eye is a typical feature in case of tropical cyclone, where as in temperate cyclone there is no such concept of ‘EYE’ associated with it.
- AREA COVERED: Temperate cyclone covers large area as compared to tropical cyclone.
- SOURCE OF ORIGIN: Tropical cyclone generally originates over water surface but the temperate cyclone originates over mid-latitude land mass.
- DIRECTION OF FLOW: Temperate cyclone generally flows eastward movement (from west to east) but there is no as such fixed movement pattern in case of tropical cyclone. Tropical cyclone generally takes the path from sea to land.
- NUMBERS: Tropical cyclone is of singular characteristic, whereas temperate cyclone flows in family.
To fight such kind of cyclones there is a need for more effective and faster information dissemination to the coastal communities with adequate provision for cyclone shelters. There is also a need for fast relief and rescue operations for the fishermen stranded in the ocean.